In vitro and in vivo comparisons of staphylococcal biofilm formation on a cross-linked poly(ethylene glycol)-based polymer coating

Poly(ethylene glycol) (PEG) coatings are known to reduce microbial adhesion in terms of numbers and binding strength. However, bacterial adhesion remains of the order of 10⁴ cm^?2. It is unknown whether this density of bacteria will eventually grow into a biofilm. This study investigates the kinetics of staphylococcal biofilm formation on a commercially produced, robust, cross-linked PEG-based polymer coating (OptiChem^®) in vitro and in vivo. OptiChem^® inhibits biofilm formation in vitro, and although adsorption of plasma proteins encourages biofilm formation, microbial growth kinetics are still strongly delayed compared to uncoated glass. In vivo, OptiChem^®-coated and bare silicone rubber samples were inserted into an infected murine subcutaneous pocket model. In contrast to bare silicone rubber, OptiChem^® samples did not become colonized upon reimplantation despite the fact that surrounding tissues were always culture-positive. We conclude that the commercial OptiChem^® coating considerably slows down bacterial biofilm formation both in vitro and in vivo, making it an attractive candidate for biomaterials implant coating.     

New Anti-infective Coatings of Surgical Sutures Based on a Combination of Antiseptics and Fatty Acids

Wound infection is a complication feared in surgery. The aim of this study was to develop new anti-infective coatings of surgical sutures and to compare the anti-microbial effectiveness and biocompatibility to the well-established Vicryl Plus^®. Synthetic absorbable PGA surgical sutures were coated with three different chlorhexidine concentrations and two different octenidine concentrations in combination with palmitic acid and lauric acid. Drug-release kinetics lasting 96 h were studied in phosphate-buffered saline at 37°C. Anti-infective characteristics were determined by measuring the change in optical density of Staphylococcus aureus suspensions charged with coated sutures over time. Microorganisms adsorbed at the surface of coated sutures were assessed on blood agar plates and coated sutures eluted for 24 h were placed on bacterial lawns cultured on Mueller–Hinton plates to prove retained anti-microbial potency. A cell proliferation assay was performed to assess the degree of cytotoxicity. Anti-infective characteristics and biocompatibility were compared to Vicryl Plus^®. A coating technology for slow-release drug-delivery systems on surgical sutures could be developed. All coatings showed a continuous drug release within 96 h. Individual chlorhexidine and octenidine coated sutures showed superior anti-infective characteristics but inferior biocompatibility in comparison to Vicryl Plus^®. We conclude that the developed anti-infective suture coatings consisting of lipid-based drug-delivery systems in combination with antiseptics are highly effective against bacterial colonization in vitro; however, drug doses have to be adjusted to improve biocompatibility.     

In vivo protein adsorption on polymers: visualization of adsorbed proteins on vascular implants in dogs

The absorption of plasma proteins is an important event at the blood-material interface, and strongly affects subsequent cellular interaction and thrombus formation. Although considerable efforts have been expended to elucidate the mechanism of protein adsorption and the role of absorbed protein layer at the blood-material interface, there has been little knowledge of how the initial adsorbed proteins are maintained or changed in a time-variant process in in vivo long-term implantation. In this study, we described detailed analyses concerning the characterization of adsorbed proteins on HEMA-styrene block copolymer surfaces (HEMA-st) and poly(ethylene oxide)(PEO) grafted Biomer® (B-PE04K) for in vivo long-term canine vascular graft implants as well as in vitro short-term experiments. Biomer vascular grafts (6 mm I.D., 7 cm in length) were fabricated by a dip coating and the luminal surface was modified with PEO grafting, HEMA-st coating, or Biomer coating (control). These surface modified grafts were recirculated for different time intervals (5, 15, 30, 60 and 120 min) using citrated canine whole blood. The grafts were then implanted in the abdominal aortas of dogs and evaluated for graft patency and protein adsorption. The adsorbed proteins (albumin, IgG and fibrinogen) were quantified using an in situ radioimmunoassay. Surface protein layer thickness was measured by transmission electron microscopy (TEM). Visualization of absorbed plasma proteins (albumin, IgG and fibrinogen) was performed with TEM using an immunoperoxidase double antibody technique. In in vitro recirculation systems, albumin and IgG showed similar Langmuir type pattern onto all test surfaces. On B-PEO4K surfaces, fibrinogen adsorption kinetics demonstrated 'Vroman effect'. The Biomer and B-PE04K grafts occluded within 1 month, while HEMA-st grafts were patent for over 3 months. Biomer and B-PE04K showed thick multilayers of adsorbed proteins, and the thickness increased with implantation periods and the composition altered with time. In contrast, HEMA-st showed a monolayer-like adsorbed protein pattern, and the composition and thickness were consistent regardless of implantation time including in vitro short-time experiments, which may attribute to less conformational change of adsorbed proteins on HEMA-st surfaces. In terms of nonthrombogenicity, the stable monolayer-like adsorbed protein layer on HEMA-st surfaces exhibited improved blood compatibility over thick multilayered adsorbed proteins on Biomer and B-PE04K surfaces.     

Polypropylene Meshes to Prevent Abdominal Herniation. Can Stable Coatings Prevent Adhesions in the Long Term?

Abdominal surgery is associated with a significant risk for incisional herniation. Hernia repair is routinely performed by implantation of synthetic meshes. Such meshes may cause serious adhesions between the implanted material and organs leading to intestinal obstruction or enterocutaneous fistulas. This study compares three knitted meshes for their capacity to prevent adhesion formation in an in vivo study. The meshes evaluated are polypropylene (Prolene^®), polypropylene coated with oxygenated regenerated cellulose—in principle—a biodegradable biomaterial (Proceed^®), and Prolene^® coated with a nondegradable copolymer of the hydrophilic building block N-vinyl pyrrolidone (NVP) and the hydrophobic building block n-butylmethacrylate (BMA). The meshes were implanted in the abdomen of rats (follow-up 7 or 30 days). After 7 days, the formation of adhesions decreased in the order: Prolene^® > NVP/BMA-coated Prolene^® > Proceed^®; after 30 days, this order changed into: Proceed^® > Prolene^® > NVP/BMA-coated Prolene^®. Both at 7 and at 30 days, Proceed^® was the only mesh surrounded by macrophage cells that contained foreign materials, presumably degradation products of the (biodegradable) surface coating. The data indicate that long-term protection of implanted meshes against excessive adhesions may be achieved through stable biocompatible hydrogel surface coatings.     

In vitro and in vivo studies of PEO-grafted blood-contacting cardiovascular prostheses

The initial step of thrombus formation on blood-contacting biomaterials is known to be adsorption of blood proteins followed by platelet adhesion. Poly(ethylene oxide) (PEO) has been frequently used to modify biomaterial surfaces to minimize or prevent protein adsorption and cell adhesion. PEO was grafted onto a number of biomaterials in our laboratory. Nitinol stents and glass tubes were grafted with PEO by priming the metal surface with trichlorovinylsilane (TCVS) followed by adsorption of Pluronic and γ-irradiation. Nitinol stents were also coated with Carbothane® for PEO grafting. Chemically inert polymeric biomaterials, such as Carbothane, polyethylene, silicone rubber, and expanded polytetrafluoroethylene (e-PTFE), were first adsorbed with PEO-polybutadiene-PEO (PEO-PB-PEO) triblock copolymers and then exposed to γ-irradiation for covalent grafting. For PEO grafting to Dacron® (polyethylene terephthalate), the surface was sequentially treated with PEO-PB-PEO and Pluronics® followed by γ-irradiation. In vitro studies showed substantial reduction in fibrinogen adsorption and platelet adhesion to the PEO-grafted surfaces compared with control surfaces. Fibrinogen adsorption was reduced by 70-95% by PEO grafting on all surfaces, except for e-PTFE. The platelet adhesion corresponded to the fibrinogen adsorption. When the PEO-grafted surfaces were tested ex vivo/in vivo, however, the expected beneficial effect of PEO grafting was inconsistent. The beneficial effect of the PEO grafting was most pronounced on the PEO-grafted nitinol stents. Thrombus formation was reduced by more than 85% by PEO grafting on metallic stents. Only moderate improvement (i.e. 35% decrease in platelet deposition) was observed with PEO-grafted tubes of polyethylene, silicone rubber, and glass. For PEO-grafted heart valves made of Dacron, however, no effect of PEO grafting was observed at all. It appears that the extent of thrombus formation on PEO-grafted biomaterials was directly related to the extent of tissue damage during implantation surgery. Platelets can be activated and form aggregates in the bulk blood, and the formed platelet aggregates may be able to deposit on the PEO monolayer overcoming its repulsive property. Our studies indicate that the testing of in vitro platelet adhesion should include adhesion of large platelet aggregates, in addition to adhesion of individual platelets. Furthermore, the surface modification methods should be improved over the current monolayer grafting concept so that the repulsive force by the grafted PEO layers is large enough to prevent adhesion of platelet aggregates formed in the bulk blood before arriving at the biomaterial surface.     

Five Types of Polyurethane Vascular Grafts in Dogs: The Importance of Structural Design and Material Selection

Five polyurethane vascular grafts with three different chemistries were investigated in terms of device function, healing characteristics and material stability in a canine abdominal aorta model for prescheduled periods of 1 and 6 months. Corvita^®-reinforced grafts, with walls made of poly(carbonate urethane) (PCU) filaments, displayed a relatively thin, uniform and partially endothelialized inner capsule with good tissue in-growth. The external polyester mesh separated from the underlying PCU wall due to the degradation of the melt adhesive between these two layers. Three types of Thoratec^® access graft exhibited a high degree of thrombus and little tissue in-growth, and were non-adhesive to both the inner and external capsules as the solid layer beneath their lumens completely blocked any transmural communication. The microporous poly(ether urethane urea) degraded extensively. Pulse-Tec^® grafts at one month also demonstrated non-adhesive properties because the external skin served as a barrier to tissue in-growth. At 6 months, its poly(ether urethane) wall displayed the most severe degradation, damaging graft structural integrity and causing significant tissue deposition in the degradation areas. This study shows the importance of multiple factors in vascular prosthesis design and demonstrates that collective and comprehensive thinking will be key in the future development of creative and novel approaches.     

Evaluation of in vivo adsorption of blood elements onto hydrogel-coated silicone rubber by scanning electron microscopy and fourier transform infrared spectroscopy

Three hydrogel formulations consisting of 2-hydroxyethyl methacrylate (HEMA) copolymerized with N-vinyl pyrrolidone (NVP) were incorporated into silicone rubber by irradiation-induced polymerization. These coatings were chosen to represent different degrees of hydrophilicity, and they changed the hydrophobic character of the silicone rubber surface to that of hydrophilic. These composite materials and the silicone rubber comparison material were used as femoral artery-to-vein (A-V) shunts and were removed at 15 min, an approximate time representative of an initial buildup stage of blood elements on test surfaces. Data obtained by scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells and fibrin at the time interval described. One-half of each specimen was used for Fourier Transform Infrared (FT-IR) analysis to provide a direct comparison of the relative amounts of protein present on the silicone rubber and the three hydrogel composite samples. The combined SEM and FT-IR analyses were performed on A-V samples from three dogs. Differences in the response of blood to the surfaces were found by the combined SEM and FT-IR analyses. The more hydrophilic a hydrogel grafted surface, the less fibrin and cellular elements were seen deposited on it. This is not interpreted as an indication of less reactivity, but is more likely due to thrombus buildup and a degree of subsequent embolization (a tearing of sections of the platelet matting away from a surface, revealing an area that again can be covered.     

In vivo protein adsorption on polymers: visualization of adsorbed proteins on vascular implants in dogs.

The absorption of plasma proteins is an important event at the blood-material interface, and strongly affects subsequent cellular interaction and thrombus formation. Although considerable efforts have been expended to elucidate the mechanism of protein adsorption and the role of absorbed protein layer at the blood-material interface, there has been little knowledge of how the initial adsorbed proteins are maintained or changed in a time-variant process in in vivo long-term implantation. In this study, we described detailed analyses concerning the characterization of adsorbed proteins on HEMA--styrene block copolymer surfaces (HEMA-st) and poly(ethylene oxide) (PEO) grafted Biomer (B-PEO4K) for in vivo long-term canine vascular graft implants as well as in vitro short-term experiments. Biomer vascular grafts (6 mm I.D., 7 cm in length) were fabricated by a dip coating and the luminal surface was modified with PEO grafting, HEMA-st coating, or Biomer coating (control). These surface modified grafts were recirculated for different time intervals (5, 15, 30, 60 and 120 min) using citrated canine whole blood. The grafts were then implanted in the abdominal aortas of dogs and evaluated for graft patency and protein adsorption. The adsorbed proteins (albumin, IgG and fibrinogen) were quantified using an in situ radioimmunoassay. Surface protein layer thickness was measured by transmission electron microscopy (TEM). Visualization of absorbed plasma proteins (albumin, IgG and fibrinogen) was performed with TEM using an immunoperoxidase double antibody technique. In in vitro recirculation systems, albumin and IgG showed similar Langmuir type pattern onto all test surfaces. On B-PEO4K surfaces, fibrinogen adsorption kinetics demonstrated 'Vroman effect'. The Biomer and B-PEO4K grafts occluded within 1 month, while HEMA-st grafts were patent for over 3 months. Biomer and B-PEO4K showed thick multilayers of adsorbed proteins, and the thickness increased with implantation periods and the composition altered with time. In contrast, HEMA-st showed a monolayer-like adsorbed protein pattern, and the composition and thickness were consistent regardless of implantation time including in vitro short-time experiments, which may attribute to less conformational change of adsorbed proteins on HEMA-st surfaces. In terms of nonthrombogenicity, the stable monolayer-like adsorbed protein layer on HEMA-st surfaces exhibited improved blood compatibility over thick multilayered adsorbed proteins on Biomer and B-PEO4K surfaces.     

Improved osteoconduction of cortical bone grafts by biodegradable foam coating

Alteration of the geometrical surface configuration of cortical bone allografts may improve incorporation into host bone. A porous biodegradable coating that would maintain immediate structural recovery and subsequently allow normal graft healing and remodeling by promoting bony ingrowth could provide an osteoconductive surface scaffold. We investigated the feasibility of augmenting cortical bone grafts with osteoconductive biodegradable polymeric scaffold coatings. Three types of bone grafts were prepared: Type I--cortical bone without coating (control), Type II--cortical bone coated with PLGA-foam, Type III--cortical bone coated with PPF-foam. The grafts were implanted into the rat tibial metaphysis (16 animals for each type of bone graft). Post-operatively the animals were sacrificed at 2 weeks and 4 weeks (8 animals for each type of bone graft at each time point). Histologic and histomorphometric analysis of grafts showed that the amount of new bone forming around the foam-coated grafts was significantly higher than in the control group (uncoated; p < 0.02). Although both foam formulations were initially equally osteoconductive, PLGA-based foam coatings appeared to have degraded at two weeks postoperatively, whereas PPF-based foam coatings were still present at 4 weeks postoperatively. While significant resorption was present in control allografts with little accompanying reactive new bone formation, PLGA-coated bone grafts showed evidence of bone resorption and subsequent bony ingrowth earlier than those coated with PPF-based foams suggesting that PPF-coated cortical bone grafts were longer protected against host reactions resulting in bone resorption.     

Evaluation of plasma polymerized hexamethylcyclotrisiloxane biomaterials towards adhesion of canine platelets and leucocytes

Silicons coated Celgard®-2400 and Silastic® membranes were prepared by plasma polymerization of hexamethylcyclotrisiloxane. The adhesion of canine platelets and leucocytes was tested by passing whole blood from the anaesthetized mongrel dog in an ex-vivo shunt system. The silicone coated Celgard and silicone coated Silastic membranes had fewer platelets and fewer leucocytes compared to those on the control Silastic membranes. Furthermore, these blood cells underwent fewer morphological changes on the silicone coated Celgard and Silastic compared to those on the control Silastic. From these observations the silicone coated biomaterials were judged to be better than the Silastic as far as the adhesion of platelets and leucocytes are concerned.     

In vitro formation of oropharyngeal biofilms on silicone rubber treated with a palladium/tin salt mixture

Adhesion of yeasts and bacteria to silicone rubber is one of the first steps in the biodeterioration of indwelling, silicone rubber voice prostheses. In this paper, silicone rubber, so-called "Groningen button," voice prostheses were treated with a colloidal palladium/tin solution to form a thin metal coat intended to discourage biofilm formation. First it was demonstrated that this treatment did not negatively affect the airflow resistance of the prostheses or induce any cytotoxicity. Subsequently, palladium/tin-treated voice prostheses were placed in a modified Robbins device together with untreated control prostheses to evaluate biofilm formation. Biofilms were formed by inoculating the device for 3 days with the total cultivable microflora obtained from an explanted, malfunctioning voice prosthesis supplemented with separately isolated yeasts (Candida albicans and Candida tropicalis). After 3 days the device was perfused three times daily with growth medium and phosphate-buffered saline. The device was allowed to drain between perfusions to better mimic the conditions in the oropharynx (moist but not always fully wetted). After 9 days the total number of bacterial and fungal colony-forming units on the prostheses were determined microbiologically, and scanning electron micrographs were taken of the valve sides. Biofilm formation was significantly less on the heavily treated palladium/tin prostheses than it was on the untreated prostheses although some ingrowing microcolonies also were observed on the treated prostheses. The spread of the biofilms was smaller on the treated prostheses than on the untreated ones.     

Viscoelastic behavior of polyurethane vascular prostheses

A method of evaluating the in vitro viscoelastic properties of microfibrous Biomer poly(ether-urethane-urea) vascular prostheses is outlined. Quasi-static and dynamic tests were carried out on Biomer grafts of diameter between 3.4 mm and 3.8 mm and wall thickness between 0.25 mm and 0.55 mm. It is shown that the quasi-static compliance of a Biomer graft may be determined from an equation relating transmural pressure, radius, and longitudinal strains in terms of the graft dimensions and material constants. The dynamic compliance spectra were evaluated as a function of the longitudinal and circumferential strains and temperature. Although the ratio of dynamic compliance to quasi-static compliance was linearly related to the logarithm of frequency it was not significantly affected by strains or temperature over the relevant ranges studied. Employing the usual assumptions of linear isotropic incremental elastic theory the dynamic elastic and viscous moduli were calculated as a function of frequency. Biomer grafts were more viscous than canine carotid and femoral arteries, especially at the higher frequencies. The variation in the ratio of dynamic to static incremental modulus with frequency was similar to that observed in the femoral arteries by Bergel (J. Physiol., 156, 458-469 (1961)).     

Biomimetic Fluorocarbon Surfactant Polymers Reduce Platelet Adhesion on PTFE/ePTFE Surfaces

We describe a series of fluorocarbon surfactant polymers designed as surface-modifying agents for improving the thrombogenicity of ePTFE vascular graft materials by the reduction of platelet adhesion. The surfactant polymers consist of a poly(vinyl amine) backbone with pendent dextran and perfluoroundecanoyl branches. Surface modification is accomplished by a simple dip-coating process in which surfactant polymers undergo spontaneous surface-induced adsorption and assembly on PTFE/ePTFE surface. The adhesion stability of the surfactant polymer on PTFE was examined under dynamic shear conditions in PBS and human whole blood with a rotating disk system. Fluorocarbon surfactant polymer coatings with three different dextran to perfluorocarbon ratios (1:0.5, 1:1 and 1:2) were compared in the context of platelet adhesion on PTFE/ePTFE surface under dynamic flow conditions. Suppression of platelet adhesion was achieved for all three coated surfaces over the shear-stress range of 0–75 dyn/cm² in platelet-rich plasma (PRP) or human whole blood. The effectiveness depended on the surfactant polymer composition such that platelet adhesion on coated surfaces decreased significantly with increasing fluorocarbon branch density at 0 dyn/cm². Our results suggest that fluorocarbon surfactant polymers can effectively suppress platelet adhesion and demonstrate the potential application of the fluorocarbon surfactant polymers as non-thrombogenic coatings for ePTFE vascular grafts.     

Efficacy of nanoporous silica coatings on middle ear prostheses as a delivery system for antibiotics: An animal study in rabbits

Nanoporous silica layers are able to host molecules and release them over a certain period of time. These local drug delivery systems for antibiotics could be a new approach in the treatment of chronic otitis media. The aim of this study was to examine the efficacy of nanoporous silica coatings on middle ear prostheses as a delivery system for antibiotics in vivo. Pseudomonas aeruginosa was inoculated into the middle ear of rabbits to induce an otitis media. The control group received coated Bioverit®II implants without antibiotics. Coated prostheses with loaded ciprofloxacin were implanted into the middle ears of the study group. After 1 week, the rabbits were sacrificed. The clinical examination as well as the microbiological and histological examinations of organs and middle ear irrigation revealed clear differences between the two groups. P. aeruginosa was detected in every middle ear of the control group and was almost completely eliminated in the study group. Organ examinations revealed the presence of P. aeruginosa in the control group and a prevention of a bacterial spread in the study group. The nanoporous silica layer as antibiotic delivery system showed convincing efficacy in induced pseudomonal otitis media in the rabbit.     

Biodegradable polyhydroxyalkanoate implants for osteomyelitis therapy: in vitro antibiotic release

Various random copolyesters of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV) and 3-hydroxybutyrate and 4-hydroxybutyrate P(3HB-4HB) were used in the construction of biodegradable, implantable rods for the local delivery of antibiotics (Sulperazone^® and Duocid^®) in chronic osteomyelitis therapy. Drug loading, type of active agent, and additional coating of the implant surface all have significant contributions to the in vitro release profile. The rate and duration of Sulperazone^® release from P(3HB-4HB) rods were controlled by the polymer/drug ratio (drug loading). The rate of drug dissolution was substantially higher than that of polymer degradation. Therefore, the release phenomenon was more dependent on drug dissolution rather than on polymer degradation or diffusion. Coating rods with the same type of polymer substantially reduced the initial burst effect observed with the uncoated rods, and significantly decreased the release rate so that the release kinetics became almost zero order. Antibiotic release from coated rods was sustained for over a period of 2 weeks at a constant rate, whereas uncoated rods released their contents in less than a week. Impregnation of Duocid^® into the hydrophobic polymer matrix yielded a rod with a smoother surface topography. The release from these rods was significantly higher than for rods loaded with Sulperazone^® and a zero order release could not be obtained with these samples.     

PPS-PEG surface coating to reduce thrombogenicity of small diameter ePTFE vascular grafts

AIMS: Patency failure of small vascular synthetic grafts is still a major problem for coronary and peripheral revascularization. Thus, three new surface coatings of small synthetic grafts were tested in an acute pig model to evaluate their thrombogenicity (extracorporeal arterio-venous shunt) and in a chronic rat model to evaluate the tissue reaction they induced (subcutaneous implantation). METHODS: In five domestic pigs (25-30 kg) an extracorporeal femoro-femoral arterio-venous shunt model was used. The study protocol included first a non-heparinized perfusion sequence followed by graft perfusion after 10,000 UI iv heparin. Grafts were perfused for 3 and 9 minutes. The following coatings were tested on ePTFE grafts: poly-propylene sulphide (PPS)--poly-ethylene glycol (PEG) (wet and dry applications) as well as carbon.Two sets of control were used, one dry and one wet (vehicle only). After perfusion grafts were examined by scanning electron microscopy for semi-quantitative assessment (score 0-3) of cellular and microthrombi deposition. To assess tissue compatibility, pieces of each material were implanted subcutaneously in 16 Wistar rats. At 2, 4, 8, 12 weeks four animals each were sacrificed for semi-quantitative (score 0-3) histologic evaluation of tissue reaction. RESULTS: In the pig model, cellular deposition and microthrombi formation increased over time. In non- heparinized animals, the coatings did not improve the surface characteristics, since they did not prevent microthrombi formation and cellular deposition. In heparinized animals, thrombogenicity was lowest in coated grafts,especially in PPS -PEG dry (p<0.05), and highest in controls. Cell deposition was lowest in PPS-PEG dry, but this difference was not statistically significant vs.controls. In the rat model,no significant differences of the tissue reaction could be shown between materials. CONCLUSION: While all coatings failed to add any benefit for lowering tissue reaction, surface coating with PPS -PEG (dry application) reduced thrombogenicity significantly (in heparinized animals) and thus appears to be promising for improving graft patency of small synthetic vascular prostheses.     

Hemocompatibility studies of surface-treated polyurethane-based chronic indwelling catheters

The objectives of this research were to evaluate and compare the interactions of several polyurethane-based central venous catheter materials with blood. Specifically, measurements of fibrinogen adsorption, platelet adhesion, kallikrein generation, and fibrinopeptide A (FPA) release were performed. The catheter materials examined in this study included: platinum-cured, 50 shore A durometer, barium sulfate-filled, silicone (SI); Tecoflex EG85A-B20 polyurethane (PU); PU catheters whose outer surface had been impregnated with ion beam-deposited silver atoms (AgI and AgII); PU catheters coated with a hydrophilic, polyacrylic acid polymer (UC); PU catheters coated with an air-cured PTFE emulsion (CS); and PU catheters coated with an aminofunctional dimethylsiloxane copolymer (JG). The time course of fibrinogen adsorption from plasma to the SI, JG, PU, and CS materials was similar, with CS exhibiting the least amount of adsorbed fibrinogen after 1 h (65±4.7 ng cm^-2) and PU the greatest (144±16.5 ng cm^-2). After 90 min of contact, AgI and AgII exhibited the greatest number of adherent platelets, levels that were approximately two to three times higher than those on the other catheter materials. With the exception of UC and PU, which caused kallikrein generation levels approximately half that of the positive (glass) control, little kallikrein formation was observed for any of the materials relative to the negative control. Finally, FPA generation was greatest using the SI, CS, and PU materials, with the latter causing the production of almost four times the amount of FPA as the negative control. This preliminary assessment of the hemocompatibility of the various catheters suggests that the surface treatments did not adversely affect their interactions with blood components; further investigations of these materials are therefore warranted in order to completely characterize their behavior prior to use in clinical situations.     

Histological and Histometric Evaluation of the Liver in Astyanax Bimaculatus (Teleostei: Characidae), Exposed to Different Concentrations of an Organochlorine Insecticide

To investigate possible morphological changes to the liver tissue of lambaris, Astyanax bimaculatus (Linnaeus, 1758), females were exposed to treatments of sublethal concentrations of the insecticide Thiodan^® for 96 hr. Treatments included three sublethal concentrations of 1.15, 2.3, and 5.6 μg L^?1 of Thiodan^® and a control group without insecticide. The action of Thiodan^® at sublethal concentrations did not affect the morphological structure of the liver as a whole, but changes in isolated locations of the hepatic parenchyma were observed. Glycogen depletion, nuclear and cytoplasmic deformation, nuclear and cytoplasmic hypertrophy, hyperemia, and cellular degeneration in liver cells at the different concentrations studied were recorded. These observed changes in the livers were greater in groups exposed to Thiodan^® in comparison to the control group. Furthermore, there was a change in the diameter of the nuclei and cytoplasm of hepatocytes in the different treatments. The groups exposed to Thiodan^® also exhibited a larger number of hepatocyte nuclei and a reduction in the amount of cytoplasm. We conclude that for the exposure period and concentrations of Thiodan^® analyzed, the morphology of hepatic tissue had a cellular adaptive response. Anat Rec, 298:1754–1764, 2015. © 2015 Wiley Periodicals, Inc.     

Platelet Adhesion and Fibrinogen Accretion on a Family of Elastin-Like Polypeptides

Previous work in our laboratory showed the potential of using a human recombinant elastin-like polypeptide (ELP) as a thromboresistant coating. In this work we investigate the use of three particular ELPs (ELP1, ELP2 and ELP4), that differ by molecular weight and number of repeating hydrophobic and cross-linking domains, as coatings to improve blood-contacting properties. All three ELPs were passively adsorbed on Mylar surfaces. Differences in water contact angle and surface concentration were found among the three ELP coatings, with the shortest polypeptide, ELP1, being the most hydrophilic and abundant on the surface (55°, 0.76 μg/cm²), followed by ELP2 (55°, 0.35 μg/cm²) and ELP4, the longest of the three (66°, 0.25 μg/cm²), respectively. The blood interactions of the ELP coatings were investigated by measuring fibrinogen adsorption and platelet adhesion in whole blood under laminar flow in a cone and plate viscometer configuration. In general, platelet adhesion to the ELP-coated surfaces was found to correlate with fibrinogen adsorption. Decreases in fibrinogen accretion and platelet adhesion were observed for ELP-coated compared to uncoated surfaces. The magnitude of the decreases was found to depend on the ELP sequence length, with ELP4 exhibiting the lowest levels of fibrinogen adsorption and platelet adhesion at 43 ± 24 ng/cm² and 113 ± 77 platelets/mm², respectively.     

Evaluation of a semi-automatic radioimmunoassay for hepatitis B surface antigen (HBsAg)

The recently developed semi-automatic Hepatube system^® was evaluated in comparison to another radioimmunoassay for the detection of hepatitis B surface antigen (HBsAg), the manual Ausria II-125 test^®. After incubation of serum in anti-HBs coated tubes, the Hepatube system uses a machine to wash the tubes and to add tracer. After a second incubation, tubes are washed again in the machine and are manually transferred to the γ counter. Two machines were used. Machine 1 had an undefined defect. Of 1490 samples tested, 69 (4.6%) gave false-positive results versus 11 (0.7%) in the Ausria II-125 test. Machine 2 had one false-positive result among 920 samples versus 5 in the Ausria II-125 test. The sensitivity was measured with reference panels from Wellcome and Abbott as well as in titration series. The Hepatube system was found to be a factor three less sensitive than the Ausria II-125 test. The Hepatube processor is easy to handle; radioactive material can be held at a distance during the whole procedure; waste material is limited and less voluminous than in the Ausria II-125 test.